Mavis Discount Tire

I'd purchased four tires from them and paid $19.66 per tire for mounting & balancing. i declined the extended warranty because I live 46 miles away and there is not a Mavis tire where I live. the tires was purchased on june 8th. I drove home and parked the (I use the car for road trips. I drive my truck daily). On june 11th I noticed that the rear driverside tire was completely flat. After inflating the tires and fully submerging them in water, I learned that the two rear tires was leaking around the valve stem. needlesstosay; the valve stem do not have to be removed to mount & balancde a tire. When I took it back to them (june 18} I was told that since I declined the extended warranty, that is not covered. I was forced to pay $116.38 for 4 TPMS's and labor. this is bulls**t! I had just bought the tires they replaced 3 months ago. they sabitoged my valve stem to exstort money. this is a theft of service. I paid because I was in a desparate situation. this is unfair buisness. I need re-emburstment.